strigi - A desktop search program

Strigi is a fast and light desktop search engine. It can handle a large range
of file formats such as emails, office documents, media files, and file
archives. It can index files that are embedded in other files. This means email
attachments and files in zip files are searchable as if they were normal files
on your harddisk.
Strigi is normally run as a background daemon that can be accessed by many
other programs at once. In addition to the daemon, Strigi comes with powerful
replacements for the popular unix commands 'find' and 'grep'. These are called
'deepfind' and 'deepgrep' and can search inside files just like the strigi
daemon can.